Projectile with expandable body



Feb. 10, 1.970 B. A. GROSS 3,494,284

PROJECTILE WITH EXPANDABLE BODY Filed March 19, 1968' 2 Sheets-Sheet 1 Feb. 10, 1970 B. A. GROSS PROJECTILE WITH EXPANDABLE BODY 5 e r m x 7w #0 P. 2 0 t W w .0 WA. 4 h 4 mm 0 S 4 K a. M m m a m M5 9- Filed March 19, 1968 fii 5 l tit US. Cl. 102-67 11 Claims ABSTRACT OF THE DISCLOSURE An explosive device wherein increased fragmentation is gained by expanding the body and filling the same with explosive material prior to detonating said material. The body is formed of spirally wound spring metal under tension so as to be capable of expanding upon release, or in the alternative, the body may be formed in any geometrical shape with nested sections taking the place of the spiral strip. The explosive may be in the form of foam, impregnated sheet or coating positioned along the entire inside surface area of the device. The hollow core of the device preferably forms a storage area for the explosive material so that the device is armed only upon expansion which in a projectile takes place in mid-air traveling to the target area.

The present invention relates to explosive devices and, more particularly, to such a device having improved fragmentation characteristics.

With the upsurge of limited and guerrilla warfare in the world today, the importance of superior conventional weapons systems to military success has once again been proved. The most successful type of weapon system in either of these situations has proved to be those that utilize fragmentation explosive devices, which are designed to be delivered and exploded in the immediate vicinity of the enemy, spraying shrapnel in all directions to inflict damage to equipment or casualties. Particularly with respect to guerrilla type warfare, there is a need today for an improved fragmentation explosive device which can be manufactured inexpensively, is lightweight and compact so that each soldier may carry increased amounts of firepower on search and destroy missions, and are armed only after delivery to the target area for safety. Also, in designing a device, it is desirable that the same form be adapted for use in any of the several explosive device forms, such as mines, grenades, rockets, bombs, and others, and most importantly, for the device to have improved effectiveness for releasing large amounts of shrapnel for any given size and amount of ordnance used.

Accordingly, it is one object of the present invention to provide an improved fragmentation explosive device having the above desirable characteristics.

It is another object of the present invention to provide an improved explosive device which is expandable from a compact or nested package to many times its original size and filled or lined with explosive material for increased fragmentation upon detonation.

A still further object of the present invention is to provide an explosive projectile and method of using the same that may be launched while in a compact package, and expanded to full size and armed while in flight to the target.

To briefly summarize the preferred structure of the present invention, there is provided an explosive device having a hollow body of metal or other shrapnel producing material which expands along its longitudinal axis to great lengths so as to provide an increased surface area for producing increased fragmentation. The body forms an extended chamber which receives the explosive material as the expansion takes place so that said explosive 3,494,284 Patented Feb. 10, 1970 ice material is detonated along the full length of the body. For safety, the explosive device is provided with a hollow core for storage of the explosive material prior to expansion of the body so that the device is not actually armed until it is intentionally expanded in anticipation of delivery to the intended target.

Several alternative forms of explosive material have been found to be particularly successful in carrying out the principles of the present invention. In the first embodiment, the explosive material may be stored within the core in a liquid state and upon release of the body for expansion, the liquid is expelled through an orifice in the form of a low density cellular explosive foam. This foam explosive device gives a particularly outstanding performance providing maximum fragmentation for a given origi nal quantity and volume of explosive material since the chamber is completely filled with said explosive material upon detonation.

Another form of the explosive material which can be used to advantage with the novel expandable construction of the present invention is in the form of impregnated extendible fabric. Such fabric is stored within the hollow body and due to a connection with the outermost part of the expandable body, is adapted to extend along the full length of the device when the body is expanded. A third alternative, for use either as a sole explosive for the device or as an additional explosive for either of the above embodiments, includes the concept of coating the inside surface of the expandable body with an explosive substance thereby further insuring that the entire inside surface area is acted upon for maximum fragmentation.

The body of metal itself is preferably fabricated from a strip of spring or similar resilient steel which is spirally wound under tension so that upon release the same expands along the longitudinal axis of the device automatically. Such a body can be held in a very limited area prior to delivery and is capable of rapid and positive expansion by removal of a holding strap across the end of the device. In an alternative embodiment, the expandable body is or may be constructed of a plurality of nestable elements which are axially spring biased so as to be adapted to expand along the longitudinal axis of the device. The elements can be formed in any cross-sectional shape, including polygonal and circular, and, as in the preferred embodiment, the explosive material is released into the chamber to arm the device upon expansion.

The explosive device of the present invention can ad vantageously be activated by a single timer which through an explosive bolt is capable of releasing the holddown strap for the expandable body. The timer is also effective to ignite a conventional time delay fuse which will detonate the explosive material within the expanded chamber after the desired time lapse.

It is contemplated that the device of the invention when used as a projectile, such as a rocket or bomb, would be released from the launcher in the compact form so that the wind resistance and other trajectory disturbing forces on the device are minimized during the first phase of delivery. Then, at a selected point prior to detonation, phase two occurs wherein the body is expanded and the explosive material is positioned within the extended chamber for arming of the device. Thus, it will be realized that with the described method not only is more accurate delivery of the rojectile possible but also that such a projectile would be much more difiicult to intercept and destroy due to its increased speed and reduced size.

Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein I have shown and described only the preferred embodiments of the invention, simply by way of illustration of the best modes contemplated by me of carrying out my invention.

As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modification in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

In the drawings:

FIGURE 1 is a cross-sectional view of an explosive device constructed in accordance with the principles of the present invention;

FIGURE 2 is an end view of the explosive device shown in FIGURE 1;

FIGURE 3 is a cross-sectional view of the device of FIGURE 1 in its expanded mode showing the extended chamber filled with foam explosive material;

FIGURE 4 is a schematic drawing showing an exemplary use of the explosive device of the present invention;

FIGURE 5 is a cross-sectional view showing an alternative embodiment of the device of the present invention;

FIGURE 6 is an end view of the device of FIGURE 5; and

FIGURES 7 and 7a are enlarged partial views of the explosive device of FIGURE 5 showing additional forms of explosive material being used, and FIGURE 7b is an enlarged perspective view showing an additional embodiment utilizing an alternative release and detonator construction.

With specific reference now to FIGURES 1-3 of the drawings, the preferred embodiment of the present invention can be described in somewhat more detail. In these figures is illustrated an explosive device 10 comprising a hollow core 11 having a rearwardly extending reduced portion 12 which in the compact or unexpanded mode shown in FIGURE 1 is surrounded by a spiral metal body 13. Enclosing the body 13 is a suitable plastic or lightweight metal protective jacket J, which is also operative to give the device 10 favorable aerodynamic properties in this unexpanded mode whereby the same may be utilized as a projectile and/or delivered through the barrel of a gun, if desired. The spiral metal body 13 is preferably constructed of a strip of spring steel helically wound on itself under tension so as to be capable of expanding outwardly when released, as shown in FIGURE 3. The inner end of the strip forming the body 13 remains suitably attached to the core 11 at its innermost turn by any number of attaching members 14, as will also be seen in FIGURE 3. Upon expansion, the strip of metal is such that each revolution seals itself with the adjacent revolution around the full periphery and along the full length of the device 10 whereby to provide an internal extended chamber for receiving of the explosive, as will now be explained.

In the preferred embodiment, the explosive is stored in a liquid state, as denoted by the reference indicia L, within the core 11. The liquid L is placed under pressure by the presence of flexible bag 15 filled with a suitable expandable gaseous propellant 16, such as carbon dioxide, adsorbed in activated carbon, alumina or other suitable material. In the rear end of the reduced portion 12 is formed an exit nozzle 17 for expulsion of the liquid in the form of foam F into the extended chamber of the body 13, as can be seen from viewing FIGURE 3.

The timed release of the liquid L from the core 11 is best accomplished at the same time that the spiral metal body 13 is released for expansion. Thus, an integral L-shaped holding strap 24] extends across the end of the device 11 and down one side with the forward end thereof being provided with an inwardly turned lug 21 for en gaging a peripheral ledge 22 on the exterior of the hollow core 11. On the opposite side of the device 10, there is preferably provided an explosive bolt 23 attached at the head end to the core 11 and which extends through the toe of the L-shaped strap 20. As shown, a conventional timer 24, which may be activated in any desired manner, such as by pulling pin P just prior to delivery to the target,

is mounted on the holding strap 20 and connected to leads 25 for exploding the bolt to allow the body 13 to spring outwardly to the expanded position of FIGURE 3. A resilient pad 26 is provided on the inside surface of the holding strap to overlie the orifice 17 in the indicated manner. Thus, when the strap 20 is ejected by the force of the expanding body 13, the liquid L is immediately released through the nozzle 17 by action of the bag 15 thereby filling the chamber with the foam F. The final turn of the body 13 has an inwardly extending skirt 28 (note FIGURE 2) forming the forward end of the device 10' thereby serving to confine the foam F to the chamber and to direct the resulting explosion outwardly against the sides of the body 13. A central aperture 29 in the skirt accommodates the nozzle end of the core 11 when the device is in the compact mode of FIGURE 1 and allows the formation of an expansion nodule N of the foam F (FIGURE 3) so that the chamber is assured of being completely filled.

A conventional controlled burning fuse 30 may be attached to the inside surface of the last or substantially last turn of the body 13 (see FIGURE 1) by a suitable fastening member 31. As shown in FIGURE 3, the fuse 30 thus projects into the explosive foam F at one end so that the device 10 is armed only when the body 13 has expanded and the foam F has filled the chamber. The other end of the fuse 30 is connected to the timer 24 for ignition in response to said timer 24. In actual practice, the fuse 30 is ignited and released by the timer 24 at the same time that the explosive bolt 23 is detonated to allow the body 13 to expand. Due to the selected length of the fuse 30, as best shown in FIGURE 2, the device 10 is thus exploded at a predetermined time after release of the expandable body; the selected time, of course, being suflicient to permit arming of the device 10 by filling with the foam F.

FIGURE 4 is a schematic showing of a novel method of use of the expandable explosive device 10 of the present invention as just described. In this system, the devices 10 are shown as projectiles or rockets 10a being launched from an airplane A in an air-to-surface operation. Thus, the projectiles are released from the aircraft A in the compact form, denoted as phase 1, so that said projectiles 10a proceed along their course toward target area T with a minimum amount of wind resistance so as to be assured of the truest possible course at the greatest speed. Upon nearing the target and as timed by the timer 24, phase 2 of the delivery occurs wherein the projectiles 10a are expanded and the extended chamber filled with the explosive foam F, thus arming said projectiles 10a as in FIGURE 3. The projectiles 10a travel the remaining distance to the target area T and explode, as denoted by phase 3. As mentioned above, the accuracy of the delivery of the projectiles 10a is greatly enhanced and the chances of successful interception are lessened by use of this concept of expansion in flight.

In an alternative arrangement of the invention shown in FIGURES 5 and 6, wherein like reference numerals are utilized to denote equivalent parts but with the suffix b for further identification, the body 13b of the device 10b comprises a plurality of individual nestable body sections 40, 41, 42, 43, 44, 45 and 46. As illustrated, each of the sections 4046 includes interlocking abutment flanges (not numbered) at the ends thereof which interlock upon expansion of the body to form an extended chamber as in the previous embodiment; the abutment flange of the outer section 46 intercepting the opposed abutment flange on the end of the next section 45 and so on until the innermost section 40 intercepts the end flange on the reduced portion 12b of the core 11b. Acting on the end of the outer section 46 is a compression spring 47 which serves to urge said section 46 forwardly upon release by the L-shaped holding strap 20b which it will be remembered is responsive to the explosive bolt 23b and the timer 2412. As the section 46 moves in this manner, the

inner sections 40-45 follow in a telescopic fashion to expand the body 13b substantially as in the previous embodiment, so that an increased area of the body 13b is acted upon to produce maximum fragmentation.

Also shown in this embodiment is an alternative arrangement of the explosive material which comprises any number of impregnated fabric rope R that can be stored in a coiled manner Within the hollow core 11b and extended outwardly with the expanding body 13b due to the fastening of the free end to the outer section 46 (note FIGURE As shown in FIGURE 6, the explosive ropes R preferably extend along each angle of the polygonally shaped sections 40-46 and are sufficiently long to accommodate the full length of the chamber. The end skirt 28b is provided as in the previous embodiment, to confine the explosive force within the device b and cause a maximum ripping and fragmentation of the body 13b as the rope R is detonated.

In FIGURE 7 is shown still another manner in which the explosive material may be applied to the device 10b of the present invention. That is, the body 13b is coated along its full inside surface area (only cutaway sections 44-46 illustrated) by a coating 50 thus further insuring that the full inside surface of the extended chamber will have explosive material thereon for full surface area fragmentation of the body 13b. It is notable that this coating 50 can be used as the sole explosive force or can be used in conjunction with either of the above forms of explosive material, such as, with the rope R as shown in FIGURE 7, to provide additional explosive force in accordance with the present invention.

In accordance with FIGURE 7a, an explosive fabric sleeve S which covers the entire inside surface area of the body 13b is utilized. The sleeve S is flexible and accordingly may also be stored in the core 11b and then stretched into position over the sections 40-46 as the body 13b expands. This embodiment of the invention (FIGURES 5- 7a) can advantageously assume any desired cross-sectional form as long as the sections 40-46 are identical and capable of nesting with each other, as shown in FIGURE 5.

As can be gained from viewing FIGURES 7 and 7a, the fusing of the device 10b of this embodiment is effected by gluing or otherwise attaching the fuse 30b to a portion 55 of the outer section 46 which does not have explosive material in any of its forms attached thereto. The fuse 30b then passes across and under the position thereof that the explosive fabric rope R (FIGURE 7) or sleeve S (FIGURE 7a) occupies when the device 10b is expanded as shown. However, said rope R or sleeve S passes over the ends of the sections and free from engagement with said fuse 30b when the device is in the compact or unexpanded form of FIGURE 5. Therefore, the device 10b is not armed until expanded whereupon due to tension in said rope R or sleeve S, said fuse 30b securely engages the underneath side of the fabric.

The alternative construction of FIGURE 7b illustrates the body 13b of circular configuration which utilizes the interior coating 50 as the sole source of explosive, as mentioned above briefly. In this embodiment, a nose cone 60 is provided that is blasted free of the core 11b by an explosive ring connection 61 in response to the timer 24b which is housed inside. The ring connection 61 has a holding portion '62 that extends across a slot 63 and holds a release lever 64 in a normal radially extending holddown position across the end face of the body 13b. The lever 64 is pivotally carried by cross shaft 65 and the aperture 29b of the end skirt 28b is keyhole shaped to accommodate not only the core 11b but also the lever 64. Thus, upon explosion of the portion 62, the lever 64 pivots about the cross shaft 65 to the axial position thereby releasing the body 13b under the resilient expanding action of the same.

A delayed action detonator or squib 70 in lieu of the fuse 30b is affixed to the interior of the core 11b and is activated for timed detonation of the explosive coating 50 only in response to the outward movement of the nose cone 60 through the actuating pin 71 and attached line 72. It will be realized that with this embodiment the outside surface area of the device 10b is clean so that the outer jacket I may be eliminated if desired.

While it is emphasized that the particular composition of the explosive material used in any of the described forms is of secondary importance and that suitable forms of explosives can be obtained from several sources and manufacturers, an explosive foam for use with this invention could be manufactured in accordance with the US. patent to Howard J. Stark 2,845,025, issued July 29, 1958, with excellent results. A suitable commercial embodiment of the rope R and the sleeve S that can be employed is obtainable under the trademark Detasheet from -E. I. du Pont de Nemours Corporation, Wilmington, -Del. A suitable embodiment of the explosive coating 50 for the purposes of this disclosure is shown, for example, by the patent to H. William Voight 3,325,317, issued June 13, 1967.

From the foregoing, it will be realized that the main advantage of the explosive device 10' over conventional devices lies in the fact that the body 13 is expandable to many times its original length so that the amount of fragmentation for any given charge of explosive material and size of device is greatly increased. That is, the overall efficiency of the device 10 is increased due to the greater surface area in contact with the explosive material which results in a larger field of flying shrapnel upon explosion. Also, the compactness of the device in the unexpanded form facilitates logistics and the device 10 is made safe for the user since it remains unarmed until the body 13 has been expanded in anticipation of delivery to the target. Further, the ability to manufacture the device from low cost and readily available components is of great benefit in the present need concerning limited and guerrilla warfare wherein great numbers of weapons must be expended to combat the elusive enemy. Also, it will be clear that the use of the explosive device 10 with the increased fragmentation properties gives superior effectiveness against human Wave attacks which are sometimes resorted to in warfare of this type.

In this disclosure, there is shown and described only the preferred embodiments of the invention, but, as aforementioned, it is to be understood that the invention is capable of various changes or modifications within the scope of the inventive concept as expressed by the accompanying claims. For example, the coating 50 may be applied in addition to the core 11 in any of the embodiments for additional explosive force of the device 10. Further, the holding portion 62 of the embodiment of FIGURE 7b could be mechanically slidable from the path of the lever 64 under action of a suitable spring, to name only one of the several Ways the release of the body 13b could be engineered.

I claim:

1. A fragmentation explosive device comprising a hollow core for storage of explosive material, an outer body of shrapnel producing material attached to said core and capable of expansion outwardly along the longitudinal axis of said device from a nested position to form an extended chamber, means for release of said explosive material into said extended chamber upon expansion, timer means for causing said body to expand, and fuse means for detonating said explosive material within said extended chamber, whereby an increased surface area of said body is provided for fragmentation when said device is exploded.

2. The combination of claim 1 wherein said explosive material within said core is in a liquid state, orifice means at the rear of said core for releasing said explosive material into said expanded body in a foam state, said extended chamber being completely filled with said explosive material, whereby detonation occurs along the length of said extended chamber for maximum fragmentation of the expanded body.

3. The combination of claim 1 wherein said explosive material is in the form of impregnated fabric, said fabric being attached to the outermost point of said body for expansion along the inside surface area of said chamber, whereby detonation occurs along the length of said extended chamber for maximum fragmentation.

4. The combination of claim 1 wherein said explosive material comprises a coating on the inside surface area of said chamber whereby detonation occurs along the length of said extended chamber for maximum fragmentation.

5. The combination of claim 1 wherein said body is formed of a strip of spring steel, said strip being spirally wound under tension with the inner end thereof attached to said core, whereby the expanding action is contained in said body itself.

6. The combination of claim 1 wherein said body includes a plurality of nestable elements, and spring means for expanding said elements to form said extended chamber.

7. The combination of claim 1 wherein the remote end of the expandable body includes a skirt means for enclosing the end of said chamber thereby retaining the explosive material within said body and causing the full explosive force to be outwardly against said body for increased fragmentation.

8. A fragmentation explosive device comprising a core, an outer body of metal attached to said core and capable of expansion outwardly along the longitudinal axis of said device to form an extended chamber, explosive material positioned along the full length of said extended chamber upon expansion, timer means for causing said body to expand, and fuse means for detonating said explosive material within said extended chamber, whereby increased 35 surface area is provided for fragmentation when said device is exploded.

9. The combination of claim 8 wherein said fuse means is positioned so as to engage said explosive material only when said body is expanded.

10. The combination of claim 8 wherein the explosive material comprises a coating positioned on the inside surface area of said extended chamber.

11. The method of delivering an explosive projectile to a target comprising the steps of releasing the projectile from the launching station in a compact form, expanding the projectile at a predetermined time after release from the launcher, providing the expanded body with an explosive material, and detonating said explosive material after a time delay from said expansion whereby the projectile is delivered over a primary distance to the target in the compact form for trajectory stability and reduced wind resistance and is detonated when expanded for maximum fragmentation of the body.

References Cited UNITED STATES PATENTS 1,817,377 8/1931 James 2443.27 2,281,213 4/1942 Thaden 1022 2,297,130 9/1942 B omar 244-327 2,426,239 8/1947 Renner 2443.26 3,282,216 11/1966 Calfee et al 1022 FOREIGN PATENTS 10,325 12/ 1912 Great Britain. 607,239 6/1926 France.

BENJAMIN A. BORCHELT, Primary Examiner J. FOX, Assistant Examiner U.S. Cl. X.R. 1022; 2443.27 

